//1.8、计算平均值:从键盘输入三个数，计算并输出平均值，保留3位小数;

#include <stdio.h>

int main()
{
    float n1, n2, n3;
    scanf("%f%f%f", &n1, &n2, &n3);
    printf("%.3f\n", (n1 + n2 + n3)/3);
    return 0;
}
